What video format do you choose for GH2 when footage should be cut with EX-1 footage at 25P?
- Shoot 24P and convert to 25P - or shoot 50i and convert to 25P - or... ??

Shoot 24P and convert to 25P. The 4% speed up is imperceptible. It's the way that Hollywood movies get converted for PAL DVDs. If you are using Final Cut on a Mac then Cinema Tools can be used to Conform the footage instantly as it just flips some bits in the header of the file to say that the frame rate is 25 rather than 24.